As a general statement, most people don’t think of the Revolutionary War as a testing ground for battlefield tactics. That assumption would not be correct. In fact, the Revolutionary War proved beyond doubt that traditional European set-piece battlefield tactics were largely ineffective against a determined enemy that was not bound by the traditional rules of war. As just one example, the extremely effective hit and run tactics used by the Minutemen to harass and deplete the British forces that marched to Lexington and Concord that were based on the tactics used by Native American fighters prove this beyond doubt. The British Regulars had no experience or training in dealing with these tactics, and they suffered as a result.

Also, in the European model, wherein gentlemen fought wars and assiduously avoided civilian casualties, it was considered impolite and improper to target the other side’s officers during the course of battle. American forces refused to comply with these rules, causing serious losses among the ranks of British officers, and the British had to adapt to these tactics also.

Another tactic adopted by American officers proved to be incredibly effective during the campaigns in the South in 1781. Brig. Gen. Daniel Morgan and Maj. Gen. Nathanael Greene, in particular, made extremely effective use of the defense in depth in carrying out their Fabian strategy during the Southern Campaigns of the Revolutionary War.

A Fabian strategy—named for its most famous practitioner, the Roman dictator, Quintus Fabius Maximus Verruscosus—avoids pitched battles and frontal assaults in favor of wearing down an opponent through a war of attrition and indirection. While avoided decisive battles, the side employing a Fabian strategy harassed the enemy through skirmishes to inflict losses, disrupt supply, and affect enemy morale. Typically, the employment of this strategy suggests that the side adopting it believes that time is on its side. George Washington was absolutely convinced that a Fabian strategy would ultimately wear down the British, and he was right.

General Nathanael Greene, who mastered the Fabian strategy in the Southern Campaign of 1781

His protégé, Greene, also believed that a Fabian strategy was the way to defeat the British. Faced with the task of defending a large swath of the South with a small army, he had little choice. His subordinate, Brig. Gen. Daniel Morgan, a rough but extremely effective amateur soldier, pioneered the use of a defense in depth at the Battle of Cowpens in January 1781, and Greene then used it on a larger scale at the Battle of Guilford Courthouse about sixty days later. That two untrained amateur soldiers could develop and use such a tactic so effective demonstrates their genius.

A defense in depth, also known as a deep or elastic defense, seeks to delay, rather than prevent, the advance of an attacker, buying time and inflicting additional casualties by trading time for space. Instead of facing an attacker with a single, strong defensive position, a defense in depth relies upon the tendency of an attack to lose momentum and cohesion over time as it covers a larger area. Thus, a defender can yield lightly defended territory in an effort to outstrip an attacker’s logistics or spread out a numerically superior attacking force. Once that attacker has lost momentum, or has become spread out to hold territory, well-planned and well-placed counterattacks can be directed at the attacker’s weak points, with the objective of causing attrition warfare or driving the attacker back to its original starting position.

A conventional defensive strategy concentrates all of a defender’s military resources in a well-defended front line, which, if breached by an attacker, would expose the remaining troops in danger of being flanked, cut off, and surrounded, and leaving lines of supply, communications, and command vulnerable to being cut.

By contrast, a defense in depth requires that defenders deploy their resources, such as prepared fortifications, earthworks, and additional forces at and well behind the front line. Once an attacker breaches the weaker initial position, it continues to meet resistance as it presses on. As the attacker penetrates further, its flanks become vulnerable, and if the advance stalls, the attacking force can find itself completely surrounded and subject to being destroyed or forced to surrender. Thus, a defense in depth is particularly effective against an attacker that can concentrate its force to attack a small number of places along an extended defensive position.

In a well-designed and properly implemented defense in depth, the defending forces fall back to a succession of prepared positions designed to inflict a heavy price on the advancing enemy while minimizing the risk of being overrun or outflanked. By delaying the enemy’s advance, a defense in depth neutralizes manpower advantages and the element of surprise, and buys time for additional forces to be readied for well-timed counterattacks. A well-designed defense in depth will use its forces in mutually supporting positions and in appropriate roles. In this scenario, poorly trained soldiers—such as militiamen—can be used in static positions at the front line, while more experienced and better-trained soldiers can form a mobile reserve, or man the ultimate defensive position to be defended. Further, a well-designed defense in depth will make good use of the natural advantages offered by terrain features and other natural obstacles such as streams, ponds, etc.

General Nathanael Greene, who mastered the Fabian strategy in the Southern Campaign of 1781

There are disadvantages associated with the defense in depth. For one thing, constantly retreating can take a toll on the morale of defending forces. Further, these forces also require a high degree of mobility to accommodate those retreats, and also the space to do so.

Morgan designed and implemented a very effective defense in depth at Cowpens that proved so effective that Greene adopted that tactic and, while he lost the Battle of Guilford Courthouse, the heavy losses his army imposed on Lord Cornwallis’ army prompted Greene to note that the British, “have met with a defeat in a victory.”